package org.usmile.algorithms.leetcode.middle;

import java.util.ArrayDeque;

/**
 * 946. 验证栈序列
 *
 * 给定 pushed 和 popped 两个序列，每个序列中的 值都不重复，只有当它们可能是在最初空栈上进行的推入 push 和弹出 pop 操作序列的结果时，返回 true；否则，返回 false 。
 *
 * 示例 1：
 * 输入：pushed = [1,2,3,4,5], popped = [4,5,3,2,1]
 * 输出：true
 * 解释：我们可以按以下顺序执行：
 * push(1), push(2), push(3), push(4), pop() -> 4,
 * push(5), pop() -> 5, pop() -> 3, pop() -> 2, pop() -> 1
 *
 * 示例 2：
 * 输入：pushed = [1,2,3,4,5], popped = [4,3,5,1,2]
 * 输出：false
 * 解释：1 不能在 2 之前弹出。
 *
 * 提示：
 * 1 <= pushed.length <= 1000
 * 0 <= pushed[i] <= 1000
 * pushed 的所有元素 互不相同
 * popped.length == pushed.length
 * popped 是 pushed 的一个排列
 */
public class _0946 {
    public static void main(String[] args) {
        int[] pushed = new int[]{1, 2, 3, 4, 5};
        int[] popped = new int[]{4, 5, 3, 2, 1};
        new _0946_Solution().validateStackSequences(pushed, popped);
    }
}

class _0946_Solution {
    public boolean validateStackSequences(int[] pushed, int[] popped) {
        ArrayDeque<Integer> stack = new ArrayDeque<>();
        int i = 0;
        for (int num : pushed) {
            stack.push(num);
            while (!stack.isEmpty() && stack.peek() == popped[i]) {
                stack.pop();
                i++;
            }
        }

        return i == popped.length;
    }
}

class _0946_Solution1 {
    public boolean validateStackSequences(int[] pushed, int[] popped) {
        ArrayDeque<Integer> stack = new ArrayDeque<>();
        int i = 0;
        int j = 0;
        while (i < pushed.length) {
            stack.push(pushed[i]);
            while (!stack.isEmpty() && stack.peek() == popped[j]) {
                stack.pop();
                j++;
            }

            i++;
        }

        return j == popped.length;
    }
}